1. Field of the Invention
The invention relates to a new and improved apparatus and method for optimizing the operating parameters of a water turbine coupled to an electrical generator. Generally speaking, the water turbine is of the type comprising a distributor having adjustable guide vanes and a runner having adjustable runner blades. The positioning of the guide vanes of the distributor is varied in accordance with the positioning of the runner blades of the runner.
2. Discussion of Background and Material Information
Water turbines are typically utilized with a generator to obtain electric power with optimum efficiency from a moving stream of water, which may have either a given or variable flow rate and velocity, and a differing height of fall. In order to attain the maximum possible efficiency in energy conversion, it is necessary to appropriately optimize the operating parameters of the water turbine (which include, among other things, the respective positionings of the guide vanes and runner blades). In particular, the positioning of the guide vanes of the distributor must be accurately adjusted for each given position of the runner blades of the runner, while taking into account other operating conditions of the turbine.
In double-regulated water turbines, such as Kaplan or tubular type water turbines, however, optimization of the operating parameters presents several difficulties in practice, and generally results in considerable expense.
A known method of determining the optimum operating parameters of a water turbine is described, for instance, in DE 935 540. The positioning of the guide vanes is set as a function of the generator output. However, with this known method, the determination of the optimum association of the distributor with a given runner position involves considerable effort and expense. To this end, field tests are performed in which different guide vane positions are operated with step-wise adjustment for a given runner blade position. This yields a so-called propeller curve. A plurality of successive propeller curves are attained across the entire power range. An enveloping curve is then placed over the propeller curves to determine, by use of the tangent points which contact the propeller curves, the optimum association between the guide vane and runner blade positions.
The following parameters are necessary to determine these propeller curves:
1. The turbine output, determined from the generator output;
2. the difference in height (i.e., the height of fall) between the upper and lower water levels; and
3. the flow (stream) of water.
The generator output and height of fall can be determined with little difficulty and with sufficient accuracy and consistency. In addition, these parameters are usually already available in the form of a permanent signal. However, accurate recording of the water flow is known to be quite difficult and thus considerably expensive. The water flow can be recorded in various ways, such as with current-meter measurements, ultrasound, flow probes, etc.
The Winther-Kennedy differential pressure method of measurement is a conventional technique for measuring the water flow and is usually used. In so doing, the differing velocity in the spiral is used according to the law of angular momentum. The measurement, made at two sampling bores in the spiral, at different radial distances from the turbine axis, yields a differential pressure which depends upon the flow (stream) of water.
There are a number of disadvantages associated with the differential pressure method of measurement. For example, great care must be taken to obtain reliable measured values. Care must be taken to provide good aeration, and silting-up of the measuring bores, etc. must be avoided. A reliable, well-functioning measurement of differential pressure is also difficult to obtain for an operational long-term measuring apparatus. Moreover, in many installations, in particular those of older construction, no differential pressure measurement connections are provided in the spiral.
If additional turbines are connected or disconnected as a result of a change in the rate of water or due to increased or reduced demand for electricity, the optimum operating parameters will change, and a new series of measurements must be performed to determine the altered optimum operating parameters.
Attempts have been made, without much success, to automate setting of the optimum operating parameters described above and thus to shorten the measuring times. Furthermore, attempts have been made to perform model experiments instead of the large-scale production trial. However, these attempts have not always resulted in optimum operating parameters which sufficiently correlate with actual practice.